One type of tape cartridge utilizes a belt that presses against the supply and take-up rolls of tape to move the tape from one roll, past a read/write assembly, and onto the other roll. The belt can be guided by a pair of corner guide rollers, and a driven pulley can move the belt along its path. The tape is maintained in tension by applying drag to the drive belt. This drag causes slight elongation of one portion of the belt, so that it tends to turn the take-up roll of tape with a slightly greater peripheral speed than the other roll of tape, to thereby produce tension in the tape.
Various schemes have been proposed for producing tension in the drive belt of a belt-driven tape cartridge. For example, U.S. Pat. No. 3,620,473 shows a friction brake shoe across which a belt must pass, to apply drag to the belt. However, the use of sliding friction against the belt can cause wear on the belt. U.S. Pat. No. 3,692,255 describes guide rollers rotating on shafts, wherein the guide rollers and shafts are constructed of materials which produce a predetermined amount of friction. However, it is difficult to obtain sufficiently high friction between a roller and its shaft while still assuring smooth rolling of the roller. This is partly because it is normally desirable to utilize polished steel shafts, which have low friction with respect to the hard plastic materials that may be utilized in constructing injection-molded rollers.